Support multiple manifest roots in all scenarios

[dkbennett]

Description of the new feature / enhancement

Up until the creation of the fonts manifest root, WinGet-Pkgs only had a single manifests root. This root was assumed in many parts of WinGet-Create, including identity of packages not including the root.

Proposed technical implementation details

Support for full manifest root for everything requires:

• Adding manifest root type to the internal tracking identity of packages.
• Determining which root a particular manifest is in instead of assuming it is manifests.
• Updating parts where the manifest root of "manifests" is assumed or default specified.
• Tests and validating scenarios for non-Manifests root types for update, locale, etc, such as for font packages.